BACKGROUND: Veterans are at elevated and increasing risk for suicide, relative to civilians. In particular, female Veterans are nearly twice as likely to die by suicide, compared to female civilians. In addition, 70% of Veterans who died by suicide did not use any Veterans Health Administration (VHA) care in the year before death. Consequently, female and non-VHA Veterans have been identified as two target populations in the VA National Strategy for Veteran Suicide Prevention. Yet most suicide prevention research has focused on VHA users and male Veterans. Knowledge is thus limited regarding whether VHA and non-VHA users differ with respect to who dies by suicide, precipitating circumstances of death, and regarding gender differences within these domains. Moreover, while mental health (MH) care offers an important opportunity to recognize and intervene upon suicide risk, knowledge is limited regarding barriers to accessing MH or suicide-specific care, particularly in relation to whether these differ by gender or VHA use. These gaps preclude determining the most effective and patient-centered means of preventing suicide among both female and male Veterans, particularly those who not using VHA care. SIGNIFICANCE/IMPACT: The present study has strong implications for understanding and preventing suicide among non-VHA users and female Veterans, both of whom have been vastly understudied. This is particularly crucial considering: (1) the 2016 Female Veteran Suicide Prevention Act, which directs VA to determine the most satisfactory and effective MH and suicide prevention programing for female Veterans; and (2) the 2019 Executive Order on a National Roadmap to Empower Veterans and End Suicide, which directs VA to work side-by-side with communities to reduce suicide among all Veterans, not only those using VHA services. This study will increase knowledge of female and male Veterans who died by suicide, including circumstances surrounding death, and the extent to which suicide decedents accessed MH care prior to death. Such knowledge can be garnered to tailor prevention efforts across Veteran groups. Moreover, by engaging with living Veterans, this study will improve understanding of Veterans? experiences and willingness to seek MH care in general and when suicidal, while also informing the extent to which their experiences, barriers, and preferences differ by gender and VHA use. This knowledge is timely and critical as VA seeks to engage more Veterans in care. INNOVATION: This study will be the first to identify factors differentiating VHA and non- VHA suicide decedents and to explore female and male Veterans? experiences and preferences for seeking help when suicidal. This study is also innovative in conceptualizing non-VHA users as comprising Veterans who were lost-to-care and who never used any VHA care. SPECIFIC AIMS: This study uses mixed-methods to compare three groups of Veterans (VHA users, never users, and lost-to-care) across three aims: (1) Identify factors that differentiate Veteran suicide decedents (e.g., circumstances of death, MH care use); (2) Examine differences in willingness to seek MH care, barriers to using MH care, and MH care experiences; and (3) Describe and compare Veterans? experiences, preferences, and barriers to help-seeking when suicidal. Gender differences will be examined across aims. METHODOLOGY: For Aim 1, probabilistic linkage of data from national sources will be combined for Veteran suicide decedents to evaluate circumstances of death (e.g., interpersonal and socioeconomic stressors, MH problems), as well as VHA MH care use (for VHA and lost-to-care decedents). For Aim 2, Veterans will be surveyed about their willingness to seek MH care, barriers to doing so, and MH care experiences. For Aim 3, qualitative interviews will explore Veterans? experiences, barriers, and preferences for seeking help when suicidal. Female Veterans will be oversampled. IMPLEMENTATION/NEXT STEPS: Intended impacts include greatly enhancing knowledge and facilitating new opportunities for implementing patient- centered, gender-sensitive suicide prevention strategies for all Veterans. Findings will be consolidated, and key stakeholder input obtained to propose actionable clinical and policy changes.